With the aid of medical systems for magnetic navigation it is possible to navigate objects and instruments which are usually used in interventional procedures, such as ablation catheters for example, in a targeted manner to a specific point within the heart or another region in the human body. Magnetic navigation allows this even without constant visual checking through x-ray and/or fluoroscopy images. A known medical system for magnetic navigation has a magnet apparatus, e.g. in the form of two large permanent magnets or electromagnets. The objects and instruments, such as catheters for example, are equipped at their tips with one and/or more magnetic elements. The magnetic fields of the magnet apparatus are activated and thereby the magnetic field vector changed by means of a control apparatus so that the object can be automatically navigated to any given positions. To this end in the case of permanent magnets these can be mechanically moved for example and in the case of electromagnets these can be supplied with power accordingly and the magnetic field changed in this way.
Imaging methods in which magnetic navigation has previously not been able to be used because of various disadvantages are primarily Computed Tomography (CT) or Magnetic Resonance Tomography (MRT). Limiting factors here for example are the closed construction of the CT scanner, which does not allow large permanent magnets e.g. a known system made by Stereotaxis, or large electromagnets of a system made by Magnetecs Systems for example to be positioned at the height of the required isocenter (e.g. the heart). With MR systems the greatest limiting factor is the strong magnetic field of the MR system, which does not allow large metal objects to be brought into the immediate vicinity. In addition an MR system also generally has a closed construction, so that here too the same limiting factor applies as with a CT scanner.
With known permanent magnets (e.g. Stereotaxis) the magnetic field vector of the magnetic field will be moved purely by a geometrical change of the magnets, which by contrast with a change of the field of electromagnets, takes a very long time. Permanent magnets can be built in an open design, so that for example good access by a doctor to the patient can be achieved; but permanent magnets are structurally very complex and large. This scarcely enables steep angulations to be set at the imaging system, e.g. C-arm (e.g. Stereotaxis Niobe system with maximum ±30° RAO/LAO). With permanent magnets there is also a danger from all magnetic objects which are bought too close to the permanent magnets.
With electromagnets the magnetic field vector of the magnetic field can be set relatively quickly and above all silently. The constructional outlay is not as great as with permanent magnets but here too steep angulations of much greater than 35° cannot be set at the imaging system. In addition no laminar air flow is possible either, which limits the use of electromagnets in a sterile environment.
The heavy weight of permanent magnets and electromagnets means that in some cases floor reinforcement measures must be taken, which renders installation difficult and expensive. In addition not every room is suitable for conversion since other devices such as air-conditioning systems, elevators etc. can be disturbed by the vibrations. Current magnets are of very large size. This is conditional on the access that one wishes to and must grant the doctor for carrying out an intervention. The large size means that the distance to the isocenter becomes very large. As a result of the inverse square law the magnetic field decreases proportionally with the increasing distance at 1/r2. To be adapted to this distance (magnet <−> ROI) enormously large magnets are needed.